Map.Entry的作用

　　　　　Set set = map.keySet();                   //keySet()            
        
        for(Iterator iter = set.iterator();iter.hasNext();)
        {
            String key = (String)iter.next();              //先获得键key
            Integer value = (Integer)map.get(key);        //再由键获得value
            
            System.out.println(key + "=" + value);
        }          
        
--------------------------------------------------------------------------
                 Set set = map.entrySet();                   //entrySet()
        
        for(Iterator iter = set.iterator();iter.hasNext();)
        {
            Map.Entry entry = (Map.Entry)iter.next();              
            String key = (String)entry.getKey();             //一次性获得键和值 key和value
            String value = (String)entry.getValue();
            
            System.out.println(key + ": " + value);
        }